package BinarySearchTree;

import sun.reflect.generics.tree.Tree;

public class BinarySearchTree {
    class TreeNode{
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }
    }
    public TreeNode root;

    public boolean search(int key)
    {
        TreeNode cur = root;
        while(cur != null)
        {
            if(cur.val > key)
            {
                cur = cur.left;
            }
            else if(cur.val < key)
            {
                cur = cur.right;
            }
            else {
                return true;
            }
        }
        return false;
    }

    public boolean insert(int val)
    {
        if(root == null)
        {
            root = new TreeNode(val);
            return true;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null)
        {
            if(cur.val < val)
            {
                parent = cur;
                cur = cur.left;
            } else if (cur.val > val) {
                parent = cur;
                cur = cur.right;
            }
            else
            {
                return false;
            }
        }
        TreeNode node = new TreeNode(val);
        if(parent.val > val)
        {
            parent.left = node;
        }
        else
        {
            parent.right = node;
        }
        return true;
    }
    //用左树的最大值或者右树的最小值替换再删除那个结点
    public void remove(int key)
    {
        TreeNode cur = root;
        TreeNode parent = null;
        while (cur != null)
        {
            if(cur.val < key)
            {
                parent = cur;
                cur = cur.right;
            } else if (cur.val > key) {
                parent = cur;
                cur = cur.left;
            }
            else
            {
                removeNode(cur, parent);
            }
        }
    }

    private void removeNode(TreeNode cur, TreeNode parent) {
        if(cur.left == null)
        {
            if(cur == root)
            {
                root = cur.right;
            } else if (cur == parent.left) {
                parent.left = cur.right;
            }
            else
            {
                parent.right = cur.right;
            }
        }
        else if(cur.right == null)
        {
            if(cur == root)
            {
                root = cur.left;
            } else if (cur == parent.left) {
                parent.left = cur.left;
            }
            else
            {
                parent.right = cur.left;
            }
        }
        else
        {
            TreeNode targetParent = cur;
            TreeNode target = cur.right;
            while(target.left != null)
            {
                targetParent = target;
                target = target.left;
            }
            cur.val = target.val;
            if(targetParent.left == target)
            {
                targetParent.left = target.right;
            }
            else
            {
                targetParent.right = target.right;
            }
        }
    }
}
